1. Field of the Invention
This invention relates to an observation apparatus which is capable of detecting a distal end position of an insertion module by using external light.
2. Description of the Related Art
Generally, considerably bright light sources are used in observation apparatuses to observe the inside or an internal wall of an observed object, such as endoscopes, to improve the observation accuracy. When the bright light quantity is maintained in the case where the member, which is inserted into the observed object to obtain observation information, is located outside the observed object, however, the observer or the test subject, who is a representative example of the observed object, may be dazzled, and the electrical energy is wasted. The visual function of the observer or the test subject may be damaged, according to the type of the light source and the light output amount. Thus, it is desired to properly control the light quantity of the light source, according to the position of the observation member for the observed object.
To meet the above demand, Japanese Patent No. 4316118 presents a technique of determining whether the insertion module is located inside the living body or outside the living body. The technique is detecting the position of the insertion module, by detecting an observed color by color detecting means attached to a distal end of the insertion module being a member used for observation, and comparing the observed color with a color signal obtained inside the living body serving as the observed object.
In Japanese Patent No. 4316118, the image observed with the distal end of the insertion module, in particular, color information thereof, is used as a determination standard for detecting the position of the insertion module. A reddish image similar to an image of the inside of the body may be obtained, however, even when the insertion module is located outside the body. In addition, color distribution is not uniform even in the body, and white or yellow regions may be observed. Thus, it is probable that the position (inside or outside of the body) of the observation module cannot be accurately detected, and the safety is not secured, or the observation is obstructed.